Apparatus and methods for efficient wireless channel usage

ABSTRACT

A multi-user uplink transmission is performed by analyzing, by a first wireless station, a spatial reuse field in a first frame, and generating, by the first wireless station, a second frame, wherein the second frame includes a spatial reuse field that is generated based on the spatial reuse field of the first frame. The first frame and the second frame are within the same transmission opportunity (TXOP) and the first frame is transmitted prior to the second frame during the TXOP.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 16/198,628,filed Nov. 21, 2018 which is a continuation of application Ser. No.15/059,237, filed Mar. 2, 2016, and issued as U.S. Pat. No. 10,172,137on Jan. 1, 2019, which claims the benefit of U.S. ProvisionalApplications No. 62/127,248, filed on Mar. 2, 2015, No. 62/264,160,filed on Dec. 7, 2015, No. 62/268,422, filed on Dec. 16, 2015, and No.62/270,469, filed on Dec. 21, 2015, the contents of which areincorporated herein by reference.

BACKGROUND 1. Technical Field

The technology described herein relates generally to wirelessnetworking. More particularly, the technology relates to clear channelassessment and a spatial reuse field.

2. Description of the Related Art

Wireless LAN (WLAN) devices are currently being deployed in diverseenvironments. Some of these environments have large numbers of accesspoints (APs) and non-AP stations in geographically limited areas. Inaddition, WLAN devices are increasingly required to support a variety ofapplications such as video, cloud access, and offloading. In particular,video traffic is expected to be the dominant type of traffic in manyhigh efficiency WLAN deployments. With the real-time requirements ofsome of these applications, WLAN users demand improved performance indelivering their applications, including improved power consumption forbattery-operated devices and increased throughput.

A WLAN is being standardized by the IEEE (Institute of Electrical andElectronics Engineers) Part 11 under the name of “Wireless LAN MediumAccess Control (MAC) and Physical Layer (PHY) Specifications.” A seriesof standards have been adopted as the WLAN evolved, including IEEE Std802.11™-2012 (March 2012) (hereinafter, IEEE Std 802.11). The IEEE Std802.11 was subsequently amended by IEEE Std 802.11ae™-2012, IEEE Std802.11aa™-2012, IEEE Std 802.11ad™-2012, and IEEE Std 802.11ac™-2013(hereinafter, IEEE 802.11ac).

Recently, an amendment focused on providing a high efficiency WLAN inhigh-density scenarios is being developed by the IEEE 802.11ax taskgroup. The 802.11ax amendment focuses on improving metrics that reflectuser experience, such as average per station throughput, the 5thpercentile of per station throughput of a group of stations, and areathroughput. Improvements may be made to support environments such aswireless corporate offices, outdoor hotspots, dense residentialapartments, and stadiums.

In some circumstances, system throughput can be improved by taking amore aggressive approach to clear channel assessment (CCA). However,increasing a CCA threshold value may result in more frequent packetcollisions and degradation of Quality of Service (QoS) of the packetdelivery. In particular, when a STA uses a more aggressive CCA thresholdand another STA in the same BSS is already transmitting data to an AP,the transmission may fail because the AP is currently receiving datafrom the other STA.

In addition, aggressive CCA may create fairness issues for legacy STAs.STAs that use more aggressive CCA may occupy and dominate a channelwhile legacy STAs determine that the channel is occupied.

The throughput gain of aggressive CCA comes from increased use ofsimultaneous transmissions. However, more simultaneous transmissionsimplies more interference during a frame exchange. Even though theeffective data rate of each individual transmission may be lowered dueto increased interference, overall throughput may increase for thesystem by allowing additional parallel transmissions or spatial reuse.The presence of increased interference is another factor limiting theutility of CCA.

SUMMARY

A method for performing a multi-user uplink transmission includesanalyzing, by a first wireless station, a spatial reuse field in a firstframe, and generating, by the first wireless station, a second frame,wherein the second frame includes a spatial reuse field that isgenerated based on the spatial reuse field of the first frame, whereinthe first frame and the second frame are within the same transmissionopportunity (TXOP) and the first frame is transmitted prior to thesecond frame during the TXOP. The first frame may immediately precedethe second frame. The first frame may be transmitted by the firstwireless station.

In an embodiment, the method further includes receiving, by the firstwireless device from a second wireless device, the first frame, whereinthe second frame is a response frame to the first frame. In anembodiment, the spatial reuse field of the second frame incudes atransmit power indication.

In an embodiment, the first frame is an initiating frame of the TXOP andthe first frame includes clear channel assessment information in thespatial reuse field while the spatial reuse field of the second frameincludes transmit power information or clear channel assessmentinformation. The the spatial reuse field of the second frame may be acopy of the spatial reuse field of the first frame.

A method for performing a multi-user uplink transmission includesassessing, by an access point, a wireless channel using clear channelassessment parameters, determining spatial reuse information based onthe assessment of the wireless channel, and generating a trigger framewherein the trigger frame includes resource allocation information forthe first wireless station and a second wireless station to participatein the multi-user uplink transmission to the access point, wherein thetrigger frame further includes the spatial reuse information, thespatial reuse information to be used by the first wireless station andthe second wireless station for setting a spatial reuse field in themulti-user uplink transmission.

In an embodiment, the spatial reuse information is located in thepayload of the trigger frame. In another embodiment, the spatial reuseinformation is located in the physical layer header of the triggerframe.

The spatial reuse information may include one or more of acceptedinterference level, transmit power, and clear channel assessment level.The spatial reuse information may be a function of a spatial use fieldof a physical layer header of the trigger frame.

A method for assessing a wireless channel includes receiving, by a firstwireless station from a second wireless station, a first frame over thewireless channe, detecting transmit power information in the firstframe, wherein the transmit power information indicates a power at whichthe second wireless station transmitted the first frame, adjusting aclear channel assessment threshold based on the transmit powerinformation detected in the first frame and a transmit power of thefirst wireless station, and performing clear channel assessment based onthe adjusted clear channel assessment threshold.

In an embodiment, the transmit power of the second wireless station islocated in a spatial reuse field of a physical layer header of the firstframe. Adjusting the clear channel assessment threshold may includedetermining a difference between the transmit power indicated in thefirst frame and the transmit power of the first wireless station, andadjusting the clear channel assessment threshold based on the determineddifference.

In an embodiment, when the transmit power of the first wireless stationis larger than the transmit power indicated in the first frame, theadjusting the clear channel assessment threshold based on the determineddifference includes subtracting the determined difference from the clearchannel assessment threshold. In an embodiment, adjusting the clearchannel assessment threshold includes determining that a color fieldindicated in the first frame is identical to a color field associatedwith the first wireless station, wherein the determining the differenceis performed in response to determining the color field indicated in thefirst frame is identical to the color field associated with the firstwireless station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless network according to an embodiment.

FIG. 2 is a schematic diagram of a wireless device according to anembodiment.

FIG. 3 illustrates an embodiment of a CCA process.

FIG. 4 illustrates overlapping coverage areas.

FIG. 5 illustrates a plurality of concurrent frames according to anembodiment.

FIG. 6 illustrates an OFDMA frame structure.

FIG. 7 illustrates a process of encoding a spatial reuse field accordingto an embodiment.

FIG. 8 illustrates STA transmissions in a TXOP according to anembodiment.

FIG. 9 illustrates STA transmissions in a TXOP according to anembodiment.

FIG. 10 illustrates STA transmissions in a TXOP according to anembodiment.

FIG. 11A illustrates STA transmissions in a TXOP according to anembodiment.

FIG. 11B illustrates STA transmissions in a TXOP according to anembodiment.

FIG. 12 illustrates MU transmissions in a TXOP according to anembodiment.

FIG. 13 illustrates MU transmissions in a TXOP according to anembodiment.

FIG. 14 illustrates MU transmissions in a TXOP according to anembodiment.

FIG. 15 illustrates MU transmissions in a TXOP according to anembodiment.

FIG. 16 illustrates MU transmissions in a TXOP according to anembodiment.

FIG. 17 illustrates a process for spatial reuse according to anembodiment.

DETAILED DESCRIPTION

Embodiments of the present disclosure relate generally to wirelessnetworking, and more particularly, to increasing an available decodetime (that is, an amount of time available to decode and process) of asymbol that has been received over a wireless network.

In the following detailed description, certain illustrative embodimentshave been illustrated and described. As those skilled in the art wouldrealize, these embodiments may be modified in various different wayswithout departing from the scope of the present disclosure. Accordingly,the drawings and description are to be regarded as illustrative innature and not restrictive. Like reference numerals designate likeelements in the specification.

FIG. 1 illustrates a wireless network according to an embodiment. Thewireless network includes an infrastructure Basic Service Set (BSS) 100of a Wireless Local Area Network (WLAN). In an 802.11 wireless LAN, theBSS provides the basic building-block and typically includes an accesspoint (AP) and one or more associated stations (STAs). In FIG. 1, theBSS 100 includes an Access Point 102 (also referred to as AP) wirelesslycommunicating with first, second, third, and fourth wireless devices (orstations) 104, 106, 108, and 110 (also referred to as STA1, STA2, STA3,and STA4, respectively). The wireless devices may each include a mediumaccess control layer (MAC) and a physical layer (PHY) according to anIEEE 802.11 standard.

Although the example of FIG. 1 shows only the BSS 100 including only thefirst to fourth stations STA1 to STA4, embodiments are not limitedthereto and may comprise BSSs including any number of STAs.

The AP 102 is a station, that is, a STA, configured to control andcoordinate functions of the BSS 100. The AP 102 may transmit informationto a single station selected from the plurality of stations STA1 to STA4in the BSS 100 using a single frame, or may simultaneously transmitinformation to two or more of the stations STA1 to STA4 in the BSS 100using either a single Orthogonal Frequency Division Multiplexing (OFDM)broadcast frame, a single OFDM Multi-User Multi-Input-Multi-Output(MU-MIMO) transmission, or a single Orthogonal Frequency DivisionMultiple Access (OFDMA) frame.

The stations STA1 to STA4 may each transmit data to the AP 102 using asingle frame, or transmit information to and receive information fromeach other using a single frame. Two or more of the stations STA1 toSTA4 may simultaneously transmit data to the AP 102 using an Uplink (UL)OFDMA frame. When the BSS 100 supports Spatial Division Multiple Access(SDMA), two or more of the stations STA1 to STA4 may simultaneouslytransmit data to the AP 102 using an UL MU-MIMO frame.

In another embodiment, the AP 102 may be absent and the stations STA1 toSTA4 may be in an ad-hoc network.

Each of the stations STA1 to STA4 and the AP 102 includes a processorand a transceiver, and may further include a user interface and adisplay device.

The processor is configured to generate a frame to be transmittedthrough a wireless network, to process a frame received through thewireless network, and to execute protocols of the wireless network. Theprocessor may perform some or all of its functions by executing computerprogramming instructions stored on a non-transitory computer-readablemedium. The transceiver represents a unit functionally connected to theprocessor, and designed to transmit and receive a frame through thewireless network.

The transceiver may include a single component that performs thefunctions of transmitting and receiving, or two separate components eachperforming one of such functions. The processor and the transceiver maybe implemented in each of the stations STA1 to STA4 and the AP 102 usingrespective hardware components, software components, or both.

AP 102 may be or may include a WLAN router, a stand-alone Access Point,a WLAN bridge, a Light-Weight Access Point (LWAP) managed by a WLANcontroller, and the like. In addition, a device such as a personalcomputer, tablet computer, or cellular phone may be able to operate asthe AP 102, such as when a cellular phone is configured to operate as awireless “hot spot.”

Each of stations STA1 to STA4 may be or may include a desktop computer,a laptop computer, a tablet PC, a wireless phone, a mobile phone, asmart phone, an e-book reader, a Portable Multimedia Player (PMP), aportable game console, a navigation system, a digital camera, a DigitalMultimedia Broadcasting (DMB) player, a digital audio recorder, adigital audio player, a digital picture recorder, a digital pictureplayer, a digital video recorder, a digital video player, and the like.

The present disclosure may be applied to WLAN systems according to IEEE802.11 standards but is not limited thereto.

In IEEE 802.11 standards, frames exchanged between stations (includingaccess points) are classified into management frames, control frames,and data frames. A management frame may be a frame used for exchangingmanagement information that is not forwarded to a higher layer of acommunication protocol stack. A control frame may be a frame used forcontrolling access to a medium. A data frame may be a frame used fortransmitting data to be forwarded to the higher layer of thecommunication protocol stack.

Each frame's type and subtype may be identified using a type field and asubtype field included in a control field of the frame, as prescribed inthe applicable standard.

FIG. 2 illustrates a schematic block diagram of a wireless device 200according to an embodiment. The wireless or WLAN device 200 canrepresent any device in a BSS, e.g., the AP 102 or any of the stationsSTA1 to STA4 in FIG. 1. The WLAN device 200 includes a basebandprocessor 210, a radio frequency (RF) transceiver 240, an antenna unit250, a storage device (e.g., memory) 232, one or more input interfaces234, and one or more output interfaces 236. The baseband processor 210,the memory 232, the input interfaces 234, the output interfaces 236, andthe RF transceiver 240 may communicate with each other via a bus 260.

The baseband processor 210 performs baseband signal processing, andincludes a MAC processor 212 and a PHY processor 222. The basebandprocessor 210 may utilize the storage device 232, which may include anon-transitory computer readable medium having software (e.g., computerprograming instructions) and data stored therein.

In an embodiment, the MAC processor 212 includes a MAC softwareprocessing unit 214 and a MAC hardware processing unit 216. The MACsoftware processing unit 214 may implement a first plurality offunctions of the MAC layer by executing MAC software, which may beincluded in the software stored in the storage device 232. The MAChardware processing unit 216 may implement a second plurality offunctions of the MAC layer in special-purpose hardware, hereinafterreferred to as “MAC hardware.” However, the MAC processor 212 is notlimited thereto. For example, the MAC processor 212 may be configured toperform the first and second plurality of functions entirely in softwareor entirely in hardware according to an implementation.

The PHY processor 222 includes a transmitting signal processing unit 224and a receiving signal processing unit 226. The PHY processor 222implement a plurality of functions of the PHY layer. These functions maybe performed in software, hardware, or a combination thereof accordingto implementation.

Functions performed by the transmitting signal processing unit 224 mayinclude one or more of Forward Error Correction (FEC) encoding, streamparsing into one or more spatial streams, diversity encoding of thespatial streams into a plurality of space-time streams, spatial mappingof the space-time streams to transmit chains, inverse Fourier Transform(iFT) computation, Cyclic Prefix (CP) insertion to create a GuardInterval (GI), and the like.

The RF transceiver 240 includes an RF transmitter 242 and an RF receiver244. The RF transceiver 240 is configured to transmit first informationreceived from the baseband processor 210 to the WLAN, and provide secondinformation received from the WLAN to the baseband processor 210.

The antenna unit 250 includes one or more antennas. When Multiple-InputMultiple-Output (MIMO) or Multi-User MIMO (MU-MIMO) is used, the antennaunit 250 may include a plurality of antennas. In an embodiment, theantennas in the antenna unit 250 may operate as a beam-formed antennaarray. In an embodiment, the antennas in the antenna unit 250 may bedirectional antennas, which may be fixed or steerable.

The input interfaces 234 receive information from a user, and the outputinterfaces 236 output information to the user. The input interfaces 234may include one or more of a keyboard, keypad, mouse, touchscreen, touchscreen, microphone, and the like. The output interfaces 236 may includeone or more of a display device, touch screen, speaker, and the like.

As described herein, many functions of the WLAN device 200 may beimplemented in either hardware or software. Which functions areimplemented in software and which functions are implemented in hardwarewill vary according to constraints imposed on a design. The constraintsmay include one or more of design cost, manufacturing cost, time tomarket, power consumption, available semiconductor technology, and soon.

As described herein, a wide variety of electronic devices, circuits,firmware, software, and combinations thereof may be used to implementthe functions of the components of the WLAN device 200. Furthermore, theWLAN device 200 may include other components, such as applicationprocessors, storage interfaces, clock generator circuits, power supplycircuits, and the like, which have been omitted in the interest ofbrevity.

Aggressive Clear Channel Assessment

Embodiments of the present disclosure relate to aggressive clear channelassessment (CCA), and how aggressive CCA states are communicated andexpressed in a wireless network. In an embodiment, a frame may includean indication of whether aggressive CCA is permitted. When a STAreceives a frame that indicates aggressive CCA is permitted, the STA mayassess the channel using an aggressive threshold value.

On the other hand, a frame may be transmitted that includes anindication that aggressive CCA is not permitted by receivers. When thisis the case, the receiving STA may perform CCA without applying anaggressive CCA threshold. For example, a default value (or anon-aggressive CCA threshold value) of −82 dBm may be used.

The processes and devices described by this disclosure may be applied tovarious forms of CCA. The present disclosure discusses power levelthreshold as the mechanism for determining channel occupancy. However,there are multiple different CCA mechanisms that are defined in variousIEEE 802.11 specifications, and persons of skill in the art willappreciate that the concepts of this disclosure can be readily extendedto and combined with other CCA criteria such as energy detection basedCCA criteria.

FIG. 3 illustrates a CCA process 300 according to an embodiment. Process300 may be performed by a STA with a pending transmission in a wirelessnetwork. As indicated in the figure, the STA may start process 300 in astate in which the channel is assessed to be IDLE.

Following initial assessment of the channel as IDLE using one or morechannel assessment mechanisms, a backoff counter is initiated, anddecremented at S302 according to a backoff time. A value of the backoffcounter is determined at S304, and when the backoff counter reacheszero, a frame may be transmitted at S306. In an embodiment, the frame isonly transmitted at S306 when the counter reaches zero and meets otherconditions of process 300 (i.e., the channel remains IDLE). Otherwise,the channel may be determined to be BUSY.

While the backoff timer of the STA of FIG. 3 is counting down, the STAmay receive a frame at S308. The frame may have been transmitted by asecond STA. When the STA performing CCA for the received frame, it maydecode some or all of the frame at S308, and determine a power in dBm ofthe received frame at S310.

The STA may then compare the power level of the frame determined at S310to a first threshold value at S312. The first threshold value is aparameter that the STA uses to assess whether a channel is clear/idleunder CCA. The first threshold value may be a first CCA threshold value,which may also be a default, or non-aggressive CCA value. For example,in an embodiment, the first threshold value may be −82 dBm for a 20 MHzPLCP Protocol Data Unit (PPDU), −79 dBm for a 40 MHz (PPDU), −76 dBm fora 80 MHz (PPDU), and −73 dBm for a 160 MHz (PPDU). However, it should berecognized that other values are possible. In another embodiment, thedefault value may be a variable value.

If the power of the frame received at S308 is lower than the first CCAthreshold value, then the CCA state is maintained at IDLE, and if noother frames are received before the counter reaches zero at S304, thenthe STA transmits a frame at S306.

If the power of the received frame exceeds the first threshold value,then process 300 may proceed to determining whether aggressive CCA isindicated in the received frame at S314. Determining whether aggressiveCCA is indicated in the received frame may include examining decodedcontent of the received frame to determine whether the STA is permittedto use aggressive CCA. For example, the STA may read one or more bits ofa frame header to determine whether the STA that transmitted the framepermitted use of an aggressive CCA scheme by other STAs (i.e., anaggressive CCA indication).

In a specific embodiment, the STA decodes an aggressive CCA indicationvalue in a High Efficiency signaling field (e.g., HE-SIG-A field). Theaggressive CCA indication may include a binary indication such aswhether or not the receiving STA is permitted to use aggressive CCA. Inother embodiments, the CCA indication may include additionalinformation, such as whether or not aggressive CCA is permitted forparticular frames of a plurality of frames.

Upon detecting that an aggressive CCA is permitted, the power of thereceived frame may be compared to a second threshold value at S318. Thesecond threshold value may be an aggressive CCA value, which is a higherpower level than the first threshold value of S312. For example, in anembodiment, the aggressive CCA values may be 3, 7, or 10 dBm higher thanthe first CCA threshold values (e.g., −79 dBm, −75 dBm, and −72 dBm).

In some embodiments, aggressive CCA operations are only performed whendata in the received frame indicates that aggressive CCA is permitted bythe receiving STA. Thus, in some embodiments, S318 is only performedwhen the power of the frame received by the STA is determined to exceedthe first threshold value at S312.

If the received power is higher than the second CCA threshold value,then the STA's CCA result is set to BUSY at S316, and the STA waitsuntil the wireless channel becomes IDLE again to initiate anotherbackoff process.

On the other hand, if the power of the received frame does not exceedthe aggressive CCA threshold value, and aggressive CCA was determined tobe allowed at S314, then the STA may perform subsequent actions. The STAmay set its CCA result to IDLE and to continue the backoff process. Ifthis action is performed, the backoff counter continues to count downuntil it reaches zero if CCA results remains in IDLE during this backoffperiod, at which point the STA transmits a frame. The second action isthat the CCA result is determined to be BUSY at S316.

In addition, at S320, the STA may encode the pending frame with dataindicating that STA that receive the frame are permitted to useaggressive CCA thresholds. In other words, the STA may set an aggressiveCCA data field in a header of the subsequently transmitted frame toindicate that aggressive CCA is permitted (i.e., CCA thresholds that arehigher than a default or traditional CCA threshold).

In a conventional process of a system that does not recognize aggressiveCCA, the power of the received frame is only compared to a singleconventional CCA threshold value in S312, and instead of performing S314when the threshold is exceeded, the process would skip to S316 anddetermine that the channel is BUSY.

In an embodiment, when a STA enables aggressive CCA for a frame asindicated in S320, the Modulation and Coding Scheme (MCS) of the framemay be set such that a target receiver of the frame can decode thepacket even under anticipated interference. On the other hand, ifaggressive CCA is not enabled at S320, then the MCS of a subsequentlytransmitted frame may be set to a scheme that has higher throughput butis more sensitive to interference. In other words, when a STA determinesthat aggressive CCA is being used, the MCS for transmitted frames may beadapted to the anticipated levels of interference.

In an embodiment, CCA sensitivity for signals occupying the primary 20MHz channel may be determined in accordance with the following Table 1.In Table 1, the CCA threshold value for aggressive CCA, which is shownas “Th₁,” is a predetermined value that is greater than −82 dBm.

The PHY may issue a PHY-CCA.indication(BUSY, {primary}) primitive if oneof the conditions listed in Table 1 below is met in an otherwise idle 20MHz, 40 MHz, 80 MHz, 160 MHz, or 80+80 MHz operating channel width. ThePHY may detect the start of a PPDU that occupies at least the primary 20MHz channel with >90% probability under the conditions listed in Table 1below within a period of aCCATime and hold the CCA signal busy(PHY_CCA.indicate(BUSY, channel-list) primitive) for the duration of thePPDU when the threshold is exceeded. Although Table 1 uses specificsignal strength values, it should be recognized that these are providedto help illustrate implementations of the present disclosure, andembodiments are not limited to these values.

TABLE 1 Operating Channel Width Conditions 20 MHz, The start of a 20 MHzNON_HT PPDU in the primary 20 MHz channel as 0 MHz, defined in OFDM PHYspecification. 80 MHz, The start of an HT PPDU under the conditionsdefined in HT PHY specification. 160 MHz, or The start of a 20 MHz VHTPPDU in the primary 20 MHz channel at as defined 80 + 80 MHz in VHT PHYspecification. The start of a 20 MHz HE PPDU in the primary 20 MHzchannel at or above −82 dBm if the PPDU indicates aggressive CCA is notallowed. The start of a 20 MHz HE PPDU in the primary 20 MHz channel ator above Th₁ dBm if the PPDU indicates aggressive CCA is allowed. 40MHz, The start of a 40 MHz non-HT duplicate or VHT PPDU in the primary40 MHz 80 MHz, channel at or above −79 dBm. 160 MHz, The start of an HTPPDU under the conditions defined in HT PHY specification. or 80 + 80MHz The start of a 40 MHz HE PPDU in the primary 40 MHz channel at orabove −79 dBm if the PPDU indicates aggressive CCA is not allowed. Thestart of a 40 MHz HE PPDU in the primary 40 MHz channel at or aboveTh₁ + 3 dBm if the PPDU indicates aggressive CCA is allowed. 80 MHz, Thestart of an 80 MHz non-HT duplicate or VHT PPDU in the primary 80 MHz160 MHz, or channel at or above −76 dBm. 80 + 80 MHz The start of a 80MHz HE PPDU in the primary 80 MHz channel at or above −76 dBm if thePPDU indicates aggressive CCA is not allowed. The start of a 80 MHz HEPPDU in the primary 80 MHz channel at or above Th₁ + 6 dBm if the PPDUindicates aggressive CCA is allowed. 160 MHz or The start of an 160 MHzor 80 + 80 MHz non-HT duplicate or VHT PPDU at or 80 + 80 MHz above −73dBm. The start of an 160 MHz or 80 + 80 MHz HE PPDU at or above −73 dBmif the PPDU indicates aggressive CCA is not allowed. The start of an 160MHz or 80 + 80 MHz HE PPDU at or above Th₁ + 6 dBm if the PPDU indicatesaggressive CCA is allowed.

The receiver may issue a PHY-CCA.indication(BUSY, {primary}) primitivefor any signal that exceeds a threshold equal to 20 dB above the minimummodulation and coding rate sensitivity (−82+20=−62 dBm) in the primary20 MHz channel within a period of aCCATime after the signal arrives atthe receiver's antenna(s), in which case the receiver does not issue aPHY-CCA.indication(BUSY, {secondary}), PHYCCA.indication(BUSY,{secondary40}), PHY-CCA.indication(BUSY,{secondary80}), orPHYCCA.indication(IDLE) primitive while the threshold continues to beexceeded.

In one embodiment, if a STA wants to access the channel with anincreased CCA threshold and transmit a first frame, the STA indicates inthe first frame that the receivers of the first frame are allowed toincrease the CCA threshold. Specifically, the STA may encode one or morebits of a header in a transmitted frame, such as a HE-SIG-A or HE-SIG-Bfield to indicate that a STA that receives the frame has permission touse aggressive CCA.

In an embodiment, even though a CCA threshold for signal detectioncriteria is increased under aggressive CCA, the aggressive CCA thresholdfor energy detection criteria is the same. In other words, whenaggressive CCA is enabled, a STA uses higher thresholds for signaldetection, but maintains the same thresholds that are used fornon-aggressive energy detection.

In an embodiment, if a STA identifies a frame while assessing thewireless medium at S308, and the frame indicates that the receiver ofthe frame is not allowed to increase a CCA threshold at S314, the STAdoes not use an increased CCA threshold value for assessing the medium.

In an embodiment, if a STA identifies more than one frame whileassessing the wireless medium at S308, the STA may decode and analyzeevery received frame. In such an embodiment, when one or more of theidentified frames has an indication that aggressive CCA is not enabled,then the STA will not use the aggressive CCA threshold value for theframe transmission. In other words, when multiple frames are receivedand decoded at S308 during a single IDLE period and any one of thereceived frames does not indicate that aggressive CCA is enabled atS314, then the STA uses the lower, non-aggressive CCA threshold value atS312 for assessing a channel, and does not perform S318 and S320 ofprocess 300.

In an embodiment, STA that are capable of performing process 300 may bepresent in the same geographic area as STA that are not capable ofperforming process 300. For example, legacy STA may be present in thesame BSS or an OBSS of a STA that can perform process 300. In such anembodiment, when a STA that can perform process 300 receives a framefrom a legacy STA that does not support process 300, the frame from thelegacy STA is interpreted as not indicating the aggressive CCA isallowed.

With reference to FIG. 3, in such an embodiment, the receiving STAreceives and decodes the frame from a legacy STA at 308. The STAperforming process 300 may determine that the frame has been sent by alegacy or non-supporting STA when the header does not include dataindicating whether aggressive CCA is permitted by receiving STA. Inthese circumstances, the receiving STA may simply determine thataggressive CCA is not allowed at S314, and not compare the power of theframe to a second aggressive CCA threshold at S318.

Such behavior may promote fairness in a system with legacy devices. Ifdevices that support aggressive CCA activate aggressive CCA in an areain which legacy devices are present, the aggressive CCA values may causethe newer devices to dominate the wireless medium. Accordingly, treatinglegacy devices as indicating that aggressive CCA is not permitted maypromote fairness between various STA.

As discussed above, a STA may indicate whether aggressive CCA ispermitted through data encoded in a header. Thus, even when a frame isreceived at S308 from a STA that supports aggressive CCA, aggressive CCAmay not be used unless the receiving STA determines that the aggressiveCCA frame data indicates that aggressive CCA is permitted at S314.

In another embodiment, referring to FIG. 1, an AP 102 indicates in aframe transmitted to one or more of associated STAs 104, 106, 108 and110 to set an aggressive CCA indication value to a specific state. Inother words, an aggressive CCA instruction may be sent from an AP 102 toassociated STAs.

When a STA that is associated with the AP 102 sends a frame, the STAsets the CCA indication value to the state that the AP has indicated,and adjust its own CCA threshold value accordingly. More specifically,the STA that receives an aggressive CCA instruction may apply anaggressive CCA threshold value at S318 when assessing the wirelessmedium. In addition, the STA may encode a frame that it transmits toindicate that aggressive CCA is permitted at S320.

In an embodiment, an AP 102 may indicate to enable or disable aggressiveCCA in the management frames in a broadcasting or multicasting mannersuch that every STA receives the aggressive CCA indication. In addition,the AP 102 may selectively indicate whether aggressive CCA is permittedon a per-STA basis.

In other words, AP 102 may indicate that aggressive CCA is permitted forone or more STA 104 and 106, while the AP 102 may indicate thataggressive CCA is not permitted for remaining STA 108 and 110. Thus, inan embodiment, aggressive CCA may be selectively based on the situationof each individual STA.

In an embodiment, aggressive CCA thresholds may be implemented for STAeven when frames are not encoded with an indication that aggressive CCAis permitted. In such an embodiment, a STA may apply the secondaggressive CCA value at S318 when assessing a wireless medium, but notencode a transmitted frame at S320. In other words, in an embodiment,S320 may not be performed.

In another embodiment, when a STA sends a frame, the STA applies an MCSlevel for the frame that has a greater margin for a given radioenvironment when the STA receives an instruction to enable aggressiveCCA compared to an MCS level that is applied when the STA determinesthat aggressive CCA is not to be applied.

In another embodiment, a number of frame transmission failures thatoccur during a predetermined time period and a predetermined zone iscompared to a threshold value. The predetermined zone may be a physicalarea, a BSS, or some other logical grouping. When the number oftransmission failures in the time period exceeds the predetermined valueand the failed frames were sent under aggressive CCA conditions, atransmitting STA may set an aggressive CCA value in a frame to instructreceiving STA that aggressive CCA is not enabled. In addition, thetransmitting STA may not apply aggressive CCA values when assessing themedium.

In another embodiment, when a first STA sends a frame that initiates aNetwork Allocation Vector (NAV), the first STA sets an aggressive CCAindication of the first frame to a state that disables aggressive CCA,and applies its own CCA threshold value accordingly.

In another embodiment, when a first STA receives a frame and the framehas valid Duration information that sets a NAV, the first STA sets orupdates a NAV if the received sensitivity level of the frame is abovethe CCA threshold level that is indicated in the frame. For example,with respect to process 300, if the first threshold value of S312 is setto −82 dBm and the second threshold value of S318 is set to −62 dBm, andif the frame is received at −70 dBm, the first STA sets or updates theNAV if frame indicates at S314 that aggressive CCA is not allowed.However, the first STA may not set or update NAV if it determines atS314 that the indication of the frame is set to a state that enablesaggressive CCA.

In another embodiment, when a first STA sets the aggressive CCAindication to a first state and sends multiple frames within a singletransmission opportunity (TXOP), the STA uses the same state throughoutthe TXOP.

In another embodiment, when a first STA transmits a first frame inresponse to a second frame within a predetermined time period, whereinthe indication of the second frame is set to a first state, theindication of the first frame is set to the same first state. In otherwords, when a STA sends back a response frame to a soliciting frame in apredetermined time, it uses the same indication value.

In another embodiment, when a first STA receives a frame and theindication of the first frame is set to a state that enables aggressiveCCA, and the duration of the frame is a known first value, the first STAtransmits a second frame based on an aggressive CCA threshold value. Inthis embodiment, the indication of the second frame is set to a statethat enables aggressive CCA and the duration of the second frame isequal to or less than the first value.

In an embodiment, an instruction to implement aggressive CCA isexpressed in a single bit in the PHY layer header part of a frame. Insuch an embodiment, the first state instructs a receiving STA to disableaggressive CCA, and the second state instructs the receiving STA toenable aggressive CCA.

In another embodiment, the indication resides in a HE-SIG-A field of aframe that follows an L-SIG field. In still another embodiment, theaggressive CCA indication may be included in the HE-SIG-B field.

In some situations, indicating that aggressive CCA is permitted byencoding a frame may reduce system performance. For example, whenmultiple STAs have frames to transmit, after aggressive CCA is indicatedin a received frame, all STAs may assess the medium under aggressive CCAconditions, creating higher levels of interference for an OBSS.Therefore, in some embodiments, a STA, such as STA A, disablesaggressive CCA in a frame that is about to transmit if the frame has alength/duration that is less than a predetermined threshold. Hence,other STAs, such as STA B, have to wait at least until the end of theframe sent by STA A and then attempt to access the medium according tothe channel access rules. This rule makes sure short frames, which areless likely to recover from interference during their short duration,would not receive possible interference from another STA if theaggressive CCA were enabled. In some other embodiments, when a STA, suchas STA A, enables the aggressive CCA in a frame that is about totransmit, other STAs, such as STA B, may attempt to access the mediumaccording to the channel access rules (such as observing mandatory IFSperiods and expiry of appropriate back-off timers) given that the framethat STA B is about to send fits the remaining time until the end of theongoing frame sent by STA A.

FIG. 4 shows a STA A, which is within coverage areas of three other STAsB, C and D. If STA A is the first node that transmits a frame with anindication that aggressive CCA is permitted, then surrounding STAs B, Cand D may all assess the medium using aggressive CCA conditions, andinclude an indication that aggressive CCA is permitted in their frames.Thus for many consecutive frames, the aggressive CCA sequence (i.e.frames with aggressive CCA permitted) could continue.

In this situation, STA A and the recipient of its frame could experiencesubstantial interference from STAs B, C and D, but each of those STAswould experience lower levels of interference. If all STAs in thescenario of FIG. 4 are transmitting according to an aggressive CCA, thenSTA A may have difficulty successfully transmitting frames. Thus, in anembodiment, a number of concurrent or consecutive frames that arepermitted to use aggressive CCA may be limited.

FIG. 5 shows an embodiment of the frames transmitted by the STAs shownin FIG. 4 that include information limiting the number of transmissionsthat enable and/or use aggressive CCA. In an embodiment, a second fieldis included in frames that show the order of the frame in an aggressiveCCA period, or similarly/equivalently it shows whether the transmissionof the subsequent frame has been based on the allowance of aggressiveCCA (or spatial reuse) from an earlier frame. In this embodiment, acounter, which indicates an order of the frame in the aggressive CCAperiod, is added to each frame so that the maximum number of concurrenttransmissions is limited. Equivalently, such a counter plays the role ofan indicator which indicates whether the transmission of the ongoingframe is based on the allowance of aggressive CCA from a first frame(i.e. a first frame that carries an aggressive CCA set to enabled), orwhether the ongoing frame has accessed the medium based on legacy mediumaccess rules (i.e. non-aggressive access rules).

Returning to the scenario of FIG. 4, when STA A starts a frametransmission with a value in a frame set to a state that enablesaggressive CCA, it may also include a second field that shows the orderof the frame in the aggressive CCA period. As shown in FIG. 5, frame 502is the first frame transmitted by STA A in a sequence, so the ordervalue in frame 502 is set to 0.

STA B receives frame 502 and performs process 300, setting theaggressive CCA indication in a transmitted frame to enabled at S320.Thus, frame 504 has a first value of 1, which indicates that aggressiveCCA is permitted by receiving frames. In addition, STA B increments thesequence counter from 0 to 1 because it is the first STA to transmit aframe (504) after receiving the initiating frame 502.

In the embodiment of FIG. 5, the maximum number of concurrenttransmissions that can occur after the initiating frame is set to two.Thus, when STA C receives frame 504 from STA B, it increments thesequence counter to 2, and transmits that data in frame 506. However,when STA D receives frame 506, in accordance with the rule that only twoconsecutive frames are permitted to use aggressive CCA, STA D does nottransmit a frame 508 that indicates aggressive CCA is permitted. Inaddition, STA D may not use aggressive CCA when assessing a medium. Inthis way, the number of simultaneous transmissions that were assessedunder aggressive CCA may be limited.

Multiple variations are possible in embodiments. The number ofconcurrent transmissions that are permitted may be different from two.In addition, the number of concurrent transmissions may be adjusted andset, for example, by an AP or by a STA according to current networkconditions. This information may be included as a field in the PHYheader of a PPDU, such as HE SIG-A.

In another embodiment, a STA may consider an amount of time that haspassed since receiving a frame from another STA when determining whetherto enable aggressive CCA, where longer times are associated withenabling aggressive CCA. For instance, a STA that receives a framecarrying the aggressive CCA indicator (and whose RA address does notcarry the identification that the STA is identified with and is not abroadcast frame) assesses the medium as follows. If the duration of theframe (obtained from the L_LENGTH field) indicates that the frame islarger than a threshold then the STA assesses the availability of themedium using the RSSI of the received frame along with the content ofthe aggressive CCA indicator (ACCA) (and in some embodiments along withthe Color field carried in the received frame). Otherwise, the STAassesses the availability of the medium according to the CCA legacyrules (based on the RSSI of the received frame).

In another embodiment, the state of aggressive CCA and the state of theorder of the frame in the aggressive CCA period are combined together.One example is to use two bits for this information. For example, 00 mayindicate that aggressive CCA is not allowed, 01 may indicate thataggressive CCA is allowed, and this frame is a first frame in asequence, 10 may indicate that aggressive CCA is allowed, and this frameis a second frame in a sequence, and 11 may indicate that aggressive CCAis not allowed, and this frame is a third frame in a sequence. Usingthis example with respect to the embodiment of FIG. 5, the first frame502 may be encoded with 01, the second frame 504 may be encoded with 10,and the third frame 506 may be encoded with 11.

With the described encoding method: (a) an unintended STA that receivesthe first frame 502 realizes that the transmitter of the first frameaccessed the medium without using the aggressive CCA rule and that usingaggressive CCA to access the medium during the reception of the firstframe is allowed, (b) an unintended STA that receives the second frame504 realizes that the transmitter of the second frame accessed themedium using the aggressive CCA rule and that using aggressive CCA toaccess the medium during the reception of the second frame is allowed,(c) an unintended STA that receives the third frame 506 realizes thatthe transmitter of the third frame accessed the medium using theaggressive CCA rule and that using aggressive CCA to access the mediumduring the reception of the third frame is not allowed (given that thesequence of frames using aggressive CCA is limited to two frames in thisexample). In another example, if the sequence of frames using aggressiveCCA is limited to one then in above example there would not be a thirdframe (i.e. only frames 502 and 504 with the same encoding as describedabove would exist and the third frame 506 would not be allowed).

In an embodiment, the indication of aggressive CCA resides in HE-SIG-Afield that follows a L-SIG field of a frame. Additional indications thatcould reside in a HE SIG-A or HE SIG-B field include: (1) an indicationof the order of the frame that uses aggressive CCA after receivinganother frame that has set aggressive CCA enabled, and (2) an indicationof the maximum number of frames that can use aggressive CCA afterreceiving a frame that has set aggressive CCA as enabled.

Spatial Reuse Field

A spatial reuse (SR) field may be included in a HE SIG-A field of a HEPPDU. This disclosure describes various ways that a SR field may beencoded and transmitted in order to ensure system fairness, particularlyfor legacy devices, and to improve system efficiency.

Orthogonal Frequency Division Multiple Access (OFDMA) is a techniquethat may be used in wireless/Wi-Fi technology in order to enhance theaggregation of multiple payloads that are destined to multiple STAswithin the same frame.

FIG. 6 shows an example of a downlink (DL) OFDMA frame 600 that istransmitted to a set of STAs. The horizontal dimension is the timedimension, which corresponds to a number of OFDM symbols, and thevertical dimension is the frequency dimension, or number of tones orsubcarriers. For a given Fast Fourier Transform (FFT) size, the numberof tones is given. However, depending on the subcarrier spacing, twoOFDM symbols with, for example, FFT=64 and FFT=256, could occupy thesame bandwidth.

A sub-band may be a horizontal partition of an OFDMA PPDU or frame wherea set of contiguous tones for a contiguous set of OFDM symbols aredesignated for a given payload whose expected destination may be a STAor a set of STAs. In the example shown in FIG. 6, the bandwidth ofindividual sub-bands are the same due to the size of the payload sent toeach STA. However, FIG. 6 is merely an example of an OFDMA frame.

The bandwidth assigned to payloads of STAs may depend on the payloadsize, the MCS, number of spatial streams that an AP determines for thesub-band transmission, and overall considerations that the AP may maketo align the length/duration of various PHY Service Data Unit (PSDU)sub-bands. Each OFDMA frame 600 has a plurality of fields that may usevarious symbols.

A header may include Legacy (L-) Short Training Field (STF), LongTraining Field (LTF) and Signal (SIG) fields 602, which are severalsymbols based on legacy 802.11 specifications. The presence of thesesymbols would make any new design compatible with legacy designs andproducts. The legacy STF, LTF and SIG symbols are modulated/carried withFFT size of 64 on 20 MHz sub-channel and duplicated every 20 MHz if theDL OFDMA PPDU has a bandwidth wider than 20 MHz.

HE SIG-A and SIG-B fields 604 are several symbols that carry informationregarding each PSDU 608 and with respect to the RF, PHY and MACproperties of the PPDU 600. This disclosure provides embodiments inwhich fields are located either in HE SIG-A and/or HE SIG-B fields 604.In an embodiment, HE SIG-A and HE SIG-B symbols can be carried ormodulated using FFT size of 64 or 256. A HE SIG-B field may not bepresent in all DL OFDM PPDUs or uplink (UL) OFDMA PPDUs.

HE STF/LTF symbols 606 are used to perform RF and PHY processing foreach PSDU 608 and/or for the whole PPDU 600. Depending on whether HESTF/LTF symbols are beamformed or not, there might be two sets of suchsymbols 606.

Each DL PSDU 608 contains the payload that is destined to a STA inaddition to MAC padding and PHY padding. Broadcast PSDU(s), located in afull-band PSDU region 608, are destined to all STAs that are associatedwith the AP. The presence and length of such PSDU(s) are indicated in HESIG-A and/or SIG-B fields 604.

The unicast PSDU(s), which is located in the sub-band region, aredestined to STAs that are associated with the AP or about to associatedwith the AP. The presence and length of a PSDU 608 in a sub-band or setof sub-bands and the one or more STA that receive of the unicast PSDUs608 are indicated in HE SIG-A and/or SIG-B fields 604. In an embodiment,one or more unicast PSDUs may be located in the sub-band PSDU region608.

The HE SIG-A field may include a Spatial Reuse (SR) field 610. The SRfield 610 may include, for example, an indication of a CCA level, aninterference level that is accepted, and a transmit power of aparticular device.

FIG. 7 shows a process 700 of encoding a SR field. In an embodiment,process 700 includes encoding a transmit power (TP) of a transmittingdevice at S702. The TP of the transmitting device may be a default orstandard power level of the device that transmits the frame, as opposedto an actual measured transmit power. In another embodiment, an actualtransmit power may be encoded in the SR field.

Transmit power information may be useful for receiving STAs to refinetheir CCA thresholds. Different STAs and APs may have different transmitpowers. For example, an APs' TP could be 20 dBm and a STA's TP could be17 dBm. In addition, transmit power may vary between individual STAs andAPs.

When there is a substantial disparity between transmit powers of an APand a STA, and in particular when an AP's TP is higher than a STA's TP,a STA on the border of an AP coverage may back off for the AP, while theAP receives the STA's signal below a CCA level e.g. −82 dBm, hence notdeferring. In other words, unequal transmit powers may lead tounfairness.

For example, consider the situation where a first CCA threshold is −82dBm, a STA has a TP of17 dBm, an Overlapping BSS (OBSS) AP has a TP of20 dBm, and where the STA receives the AP's signal at −80 dBm. Due toreciprocity, the path loss between the STA and the AP is the same inboth directions, but due to the lower TP of the STA, the AP receives theSTA's signal at −83 dBm.

As a result, the AP ignores reception of the STA's signal, so that themedium is assessed as IDLE despite presence of the STA's frame. Thiscauses unfairness in terms of competition to access the medium betweenthe STA and the AP.

Since legacy frames do not include an indication of the TP in a PPDU,there is no mechanism in legacy fields for receiving STA to consider apossible TP imbalance between a receiving STA and a transmitting STA toavoid possible channel access unfairness. However, by including transmitpower in HE SIG-A symbols, it is possible to improve the CCA procedureand prevent such unfairness.

In an embodiment, a STA that receives a frame with a legacy CCAthreshold may refine the medium access availability considering the RSSIof the received frame and the difference between its own TP and the TPindicated in the SIG-A of the received frame.

In an embodiment, a STA with a larger TP may consider a more sensitiveCCA threshold value compared to CCA values of −82/−79/−76 dBm (i.e., thelegacy CCA thresholds for 20 MHz, 40 MHz and 80 MHz received bandwidthrespectively) while receiving a HE frame. In one embodiment, if a STAwith a transmit power TP1 receives an HE frame with SR field indicatinga transmit power of TP2, where TP1=TP2+X dB and X>0, the STA reduces itsCCA thresholds by X dB. With respect to default values, the CCAthresholds would be CCA=−82−X dBm, −79−X dBm, or −76−X dBm (for 20 MHz,40 MHz and 80 MHz received bandwidth respectively) instead ofCCA=−82/−79/−76 dBm. In one embodiment, if a STA with TP1 receives an HEframe with a SR field indicating TP2, where TP1=TP2+X dB and X>0, theSTA should reduce its CCA thresholds by X dB, where X is the differencein TP values.

A STA with a smaller TP may consider a less sensitive CCA instead of adefault CCA=−82/−79/−76 (i.e. the legacy CCA thresholds for 20 MHz, 40MHz and 80 MHz received bandwidth respectively) while receiving a HEframe. In one embodiment, if a STA with TP1 receives an HE frame with SRfield indicating TP2, where TP2=TP1+X dB and X>0, the STA may increaseCCA by X dB. With respect to default CCA thresholds, the CCA would be−82+X dBm, −79+X dBm, or −76+X dBm instead of −82/−79/−76 dBm (for 20MHz, 40 MHz and 80 MHz received bandwidth respectively).

One example of SR information in a physical layer header is Color fieldof a frame. A Color field identifies a BSS to which a transmitter of theframe belongs. So, if a STA identifies a start of a frame whileassessing a wireless medium, the STA may check the Color field of theframe.

In some embodiments, a HE STA that receives a HE PPDU that carries SRfield with TP content in the HE SIG-A and a Color field in HE SIG-A, mayapply a different CCA threshold to evaluate the availability of themedium considering the Color field and a TP difference. Specifically, areceiving STA may consider whether the Color field in the received frameis the same as any of the Color fields that the STA is associated with,and the difference between the TP of the transmitter of the frame andthe TP of the receiving device.

A STA may use the Color field in its evaluation of the availability ofthe medium and CCA rules. In an embodiment, if the Color fieldinformation is the same as the Color of the receiving STA (or any of theColor values that the receiving STA is identified or associated with),the STA assesses the wireless medium as BUSY. However, if the Colorfield information is different from the Color of the receiving STA (orany of the Color values that the receiving STA is identified orassociated with), the STA may compare the received signal strength witha threshold value (e.g, OBSS_PD), and assesses the wireless medium asBUSY only if the received signal strength is above the threshold value.In other words, a STA may preferentially assess the wireless medium asBUSY when a frame is received from the same BSS to which the STA belongscompared to a frame from a different BSS.

However, as Color subfield is separately included in the physical layerheader part, the SR field does not necessarily imply Color subfieldinformation.

In an embodiment in which a HE STA with a transmit power TP1 thatreceives a HE PPDU that carries SR field with a TP field indicating apower of TP2 and a Color field in a HE SIG-A field, where TP1=TP2+X dBand X>0, the STA reduces its CCA thresholds by X dB if the Color fieldin the received frame is equal to one of the Color values that thereceiving STA is associated or identified with. Specifically, the CCAthresholds would be −82−X dBm, −79−X dBm, or −76−X dBm instead of−82/−79/−76 dBm (for 20 MHz, 40 MHz and 80 MHz received bandwidthrespectively).

In an embodiment in which a HE STA with a transmit power TP1 thatreceives a HE PPDU that carries SR field with a TP field indicating apower of TP2 and a Color field in a HE SIG-A field, where TP1=TP2+X dBand X>0, the STA may reduce its CCA thresholds by X dB if the Colorfield in the received frame is different from any of the Color valuesthat the receiving STA is associated with.

In an embodiment in which a HE STA with a transmit power TP1 thatreceives a HE PPDU that carries SR field with a TP field indicating apower of TP2 and a Color field in a HE SIG-A field, where TP1=TP2-X dBand X>0, the STA may increase its CCA thresholds by X dB if the Colorfield in the received frame is equal to one of the Color values that thereceiving STA is associated with. Specifically, the CCA thresholds wouldbe CCA=−82+X dBm, −79+X dBm, or −76+X dBm instead of CCA=−82/−79/−76 dBm(for 20 MHz, 40 MHz and 80 MHz received bandwidth respectively).

In an embodiment in which a HE STA with a transmit power TP1 thatreceives a HE PPDU that carries SR field with a TP field indicating apower of TP2 and a Color field in a HE SIG-A field, where TP1=TP2-X dBand X>0, the STA may increase its CCA thresholds by X dB if the Colorfield in the received frame is different with any of the Color valuesthat the receiving STA is associated with.

In the set of TP and Color rules described above, a HE STA may determinethe availability of the wireless medium or may revise the status of theavailability of the wireless medium after receiving a HE SIG-A field. Inlegacy systems, the availability of the wireless medium may be decidedafter receiving STF/LTF symbols in the legacy portion of the PHY header.

In an embodiment, a HE STA may determine the status of the medium to beIDLE or BUSY after receiving the legacy portion of the frame. However, aSTA may revise the medium status after receiving a HE SIG-A part of theframe that carries SR and Color fields.

In another embodiment, a HE STA that receives a HE PPDU may determinethat the medium is BUSY regardless of the RSSI of the received frameuntil it has processed and successfully decoded the HE SIG-A portion ofthe frame. Afterwards, the HE STA may determine whether the medium isBUSY or IDLE based on one or more of: (a) the RSSI of the receivedframe, (b) the difference in the TP of the STA and the TP indicated inthe SR field of the SIG-A of the received frame, and (c) whether theColor field carried in the HE SIG-A of the received frame is equal toany of the Color values that the STA is associated with.

Returning to FIG. 7, a process 700 of encoding a SR field may includeencoding an indication of an allowed interference level (e.g., ILA) atS704. For example, consider a scenario in which a first STA A sends a HEPPDU to a second STA B, and a third STA C is an unintended recipientthat receives the frame.

In one embodiment, the ILA subfield indicates the interference levelallowed at transmitting STA A, since STA A may be expecting responseframes from STA B. In such an embodiment, STA C may use such informationto decide whether to perform SR, for example by assuming the medium isavailable despite receiving the frame, or to assume the medium is BUSY.

In another embodiment, the ILA subfield in frame that is sent by STA Aindicates the level of interference that intended recipient STA B cantolerate. This is possible, for example after STA A has received ILAcontent from STA B in an a priori response frame.

A CCA level may be encoded at S706. One possible implementation for theCCA sub-field in a HE SIG-A field is that each STA indicates the CCAlevel (that it uses or it has used to evaluate the medium availabilityin the immediate past) in the CCA subfield of the SR field of HE SIG-Aof the outgoing frame. For instance, if a STA uses a CCA threshold of−79 dBm in a process 300 of assessing the medium, then it would indicatethat CCA level of −79 dBm in the SR field of the HE SIG-A of the HEframe it sends.

In some embodiments, if a STA uses a CCA of −82/−79/−76 dBm (legacy CCAthresholds for 20 MHz, 40 MHz, and 80 MHz frames, respectively) toevaluate the availability of the medium, the STA may not report the CCAthreshold since these CCA thresholds are the default values. Thus, in anembodiment, the lack of a CCA subfield in a SR field is interpreted asthe STA using default CCA values. However, in another embodiment, a HESTA may report default CCA thresholds in a CCA subfield of a SR field ofHE SIG-A.

In some embodiments, if a STA uses a CCA threshold value larger than−82/−79/−76 dBm to evaluate the availability of the medium, the STAreports the CCA threshold value. The adapted CCA threshold informationmay be used by other STAs to refine their own CCA thresholds. Inparticular, if a HE STA uses a CCA value other than the default valuesand indicates such CCA threshold in a frame that is about to transmit,the neighboring STAs may benefit from knowing the CCA value to adjusttheir own CCA values accordingly during the reception of the frame.

A SR part of a HE SIG-A field has a limited number of bits. Thus, eventhough process 700 shows several indications being encoded in an SRfield, some embodiments may only use a portion of those indications. Forexample, in one embodiment, only one of S702 and S706 is performed. Inother words, in an embodiment, the SR field may carry one or the otherof CCA or TP data. Other variations are possible.

In a specific example, the SR may include an indication subfield and avalue subfield, where the indication subfield indicates what type ofcontent appears in the value subfield. In one example, the SR values are[(indication, 1 bit), (value, X bits)], where if the value is 0 then thevalue carries TP and if the value is 1 then the value carries CCA, e.g.(0,TP) or (1,CCA). In another example, the indication has 2 bits wherethe SR values are [(indication, 2 bits), (value, X bits)]. In anembodiment, TP, CCA, ILA etc. can be carried in the value subfield, e.g.(00,TP), (10,CCA), (01,ILA), (11,SRTBD) where ILA is the interferencelevel allowed and in the SRTBD other relevant SR contents may bepresent.

In another embodiment, a few bits are assigned to each of the SRcontents (CCA, TP, and ILA etc), so that SR field contents are TP (Xbits), CCA (Y bits), ILA (Z bits), and X, Y and Z may be 1-3 bits each.In such embodiment, each value for the TP would be equivalent to atransmit power or a range of transmit power, and each value for the CCAwould indicate a specific CCA value (or a range of values) or it wouldindicate a difference from reference CCA value (or a range of values).

In another embodiment a CCA level and TP are indicated jointly in the SRfield of SIG-A. In such an embodiment, CCA and TP may be representedrelative to their default or reference values or by an absoluteindication.

In one embodiment of relative joint indication of CCA and TP, a tableindicates TP and CCA thresholds relative to default CCA and TP values.Each entry of such table would indicate a level of deviation between theSTAs actual CCA and TP values and the default CCA and TP values.

In such an embodiment, each row of a table indicates that the STAoperates with X dB less power compared to a default or reference TP andoperates with Y dB increase to a default or legacy CCA threshold.Specifically, the default CCA thresholds may be −82/−79/−76 dBm for20/40/80 MHz bandwidths respectively.

In an embodiment, a limited range of X and Y values are covered so thata few bits are used to express all the entries in such a table. Anexample of such table could be: (TP, CCA) represented by 000, where TPis a reference transmit power known to all STAs (e.g. 20 dBm) and CCA isa reference CCA threshold for a reference bandwidth such as −82 dBm for20 MHz bandwidth. With such reference, an example of encoding is asfollows: (TP-3, CCA) represented by 001, (TP, CCA-3) represented by 010,(TP-3, CCA-3) represented by 011, (TP-6, CCA-3) represented by 100,(TP-3, CCA-6) represented by 101, (TP-6, CCA-6) represented by 110, etc.In this example the unit for CCA and TP is dBm and the unit of increaseor decrease in CCA and TP values is dB, e.g. (TP-3, CCA-3) indicates TP(in unit of dBm)−3 dB and CCA (in unit of dBm)−3 dB. In the aboveexample, values of 3 dB and 6 dB are used for X and Y, but in otherembodiments, other values for X and Y can be used, such finergranularity of 1 dB or 2 dB (instead of 3 dB in above).

In one embodiment of joint indication of CCA and TP values, a tableindicates TP and CCA values, and values are presented in both relativeand absolute terms. In the table, a CCA value is relative to the defaultvalue and a TP value is an absolute or reference value or range ofvalues. Each entry of such a table may indicate how much a STA's CCAvalue deviates from a default CCA value, as well as the absolute valueor range of values for CCA.

In an embodiment, each row of the table indicates that the STA operateswith X dBm TP and operates with Y dB increase in its CCA threshold(compared to the default values −82/−79/−76 dBm for 20/40/80 MHz). Anexample of such table is: (TP<17 dBm, CCA) represented by 000, (TP<17dBm, CCA-3 dB) represented by 001, (TP=17 dBm, CCA) represented by 010,(TP=17 dBm, CCA-3 dB) represented by 011, (TP=20 dBm, CCA) representedby 100, (TP=20 dBm, CCA-3 dB) represented by 101, (TP=20 dBm, CCA-6 dB)represented by 110, etc. This in essence is quantizing a two-dimensionalregion of CCA-axis and TP-axis (where CCA is in reference to a CCAthreshold for a reference bandwidth, such as −82 dBm for 20 MHz, and TPis in reference to a reference transmit power such as 20 dBm) where eachnon-overlapping bin/region of CCA and TP is encoded by a sequence ofbits and a device, e.g. an AP, communicates the encoding to all otherdevices within its vicinity. In some embodiments, the above encodingscheme indicates the TP and CCA that the sender of the frame (thatcarries the encoding) operates based on. In other embodiments, the aboveencoding scheme indicates the TP and CCA that the sender of the framerequests other STAs to operate using the indicated CCA and TP values,e.g. an AP requests its associated STAs to use the indicated CCA and TPwhile attempting to access the medium.

The transmit power that a STA or AP uses may be regulated in somejurisdictions. For instance, in one regulatory jurisdiction the maximumallowed TP for a STA or AP might be TP1 while in another regulatoryjurisdiction the maximum allowed TP for a STA or AP might be TP2. Due tosuch restrictions, in some embodiments where a relative or absoluteindication for TP is used, the relative or absolute TP value may bedefined relative to the maximum allowed TP of the jurisdiction in whichthe STAs or APs reside. In an embodiment, a STA or AP that operates in aregulatory jurisdiction is aware of the applicable regulatoryrestriction on the transmit power and would translate the relative orabsolute TP indications (such as in above embodiments) with reference tothe maximum TP (or other regulatory parameters) that is allowed in theregulatory jurisdiction in which they reside.

FIG. 8 shows an embodiment in which a first HE STA1 and a second HE STA2are communicating during a TXOP. In the embodiment of FIG. 8, a SR fieldof a HE PPDU may carry either one of a TP value or a CCA value, but notboth. In FIG. 8, first STA initiates the TXOP and is the TXOP owner.Meanwhile, second STA responds to the PPDUs 812, 814 and 816 of thefirst STA with block acknowledgments (BAs) in frames 822, 824 and 826,respectively.

The first STA sets the SR field in the first frame 812, which initiatesthe TXOP, to indicate a CCA value. In another embodiment, if the STAuses default CCA values, the first STA may set the SR field in the firstframe 812 to indicate a TP value. For the subsequent frames in the TXOP,the first STA may set the SR field to CCA indication or TP indication.Thus, in the embodiment of FIG. 8, a CCA value is always included in thefirst PPDU 812 of a TXOP, while remaining PPDUs of the same TXOP mayinclude a CCA value or a TP value.

In an embodiment, the unintended STAs that receive two or more HE PPDUsfrom the TXOP-owner may gather the CCA and TP values from the TXOP-ownerin order to better perform SR given these two or more values. The SRvalues may include one or more of CCA, TP and ILA values. That is, STAsother than intended recipient STA2 may use information in the SR fieldsof PPDUS 812, 814 and 816 to improve network performance.

Meanwhile, a receiving STA does not perform CCA before transmitting ACKframes such as block ACK frames (BA) in response to the PPDUs.Accordingly, the second STA does not have a CCA value to report for theTXOP. However, as indicated in frames 822, 824 and 826, the STA maytransmit SR data in response frames.

In such an embodiment, the second STA may include a TP value or an ILAvalue in the SR field of one or more response frame. If the STAindicates its TP, other STAs may use that information to more accuratelymeasure how much interference affects the STAs. Thus, in an embodiment,the second STA may set the SR field in the response frames to indicateTP.

After one or more of a TP value, an ILA value and a CCA value isencoded, a frame that includes an SR field is transmitted at S708. Eachof the values that are included in the SR field may be used whenassessing whether a channel is clear and/or clear channel assessmentparameters (e.g., one or more CCA thresholds, TP of the transmittingSTA, etc.).

Spatial Reuse Fields within the Same TXOP

The SR field is related with CCA threshold adjustment of a STA when theSTA assesses a wireless medium. Therefore, the SR field value isdetermined when a STA assesses a wireless medium.

There are several situations in which a STA transmits frames withoutperforming channel assessment. One such situation is illustrated in FIG.9.

In the example of FIG. 9, STA1 has frames to send to STA2, and thus,STA1 performs channel assessment. After STA1 assesses the wirelessmedium as IDLE during a CCA evaluation, STA1 transmits a first frame 912to STA2, and the first frame sets a TXOP for a duration of T_TXOP. Afterthe TXOP duration is set, STA1 can transmit multiple frames in the sameTXOP if there is more than one frame pending.

If the transmit queue of STA1 includes additional frames 914 and 916 andthe duration of transmission of those frames plus the duration of anyexpected acknowledgement frame (e.g., BA) is less than the remainingTXOP duration, then STA1 may transmit the additional frames apredetermined time (T1) after the completion of the immediatelypreceding frame without repeating channel assessment.

Therefore, before transmitting second frame 914 and third frame 916,STA1 may not need to perform CCA. Moreover, after STA1 completes its ownframe transmissions, STA1 may solicit an acknowledgement frame (BA) 926from STA2. In this case, STA2 may transmit the acknowledgement frame 926a predetermined time (T1) after receiving soliciting frame 916 withoutperforming channel assessment.

Therefore, while STA1 is aware of the CCA performed prior totransmitting frame 912, STA1 does not have CCA information for CCAsperformed for subsequent frames 914 and 916. Similarly, STA2 does notperform CCA before transmitting BA frame 926, so STA2 does not have CCAdata for that transmission.

Therefore, in terms of indicating a SR field in the physical layerheader of each frame, which is related with CCA threshold adjustment ofSTA1/2 when the STAs assess the wireless medium, STA1 can figure out theSR field for first frame 912 because STA1 performs CCA (channelassessment) right before first frame 912. However, STA1 does not have acorrect/accurate SR field value for frames 914 and 916 because STA1transmits frames 914 and 916 without performing CCA. Similarly, STA2does not have a correct/accurate SR field value for BA frame becauseSTA2 transmits BA without performing CCA.

Described herein are several embodiments that are directed to populatingdata in an SR field of frames that are not directly associated with animmediately preceding CCA procedure. In an embodiment, when a STAtransmits a frame without performing CCA within a TXOP, the contents ofthe SR field in the physical layer header of the frame are determinedbased on the most recent CCA threshold status within the TXOP. Inanother embodiment, a default value may be used for the SR field.

Multiple embodiments of determining contents of an SR field arepossible, and particular embodiments may be more appropriate forspecific situations.

In an embodiment, when a STA transmits an HE frame without performingCCA within a TXOP, the SR field of the HE frame may be based on the mostrecent CCA threshold status within the TXOP.

In an embodiment, all HE frames transmitted by a STA within the sameTXOP have the same SR field value until the STA performs another CCA.

In an embodiment, if a STA transmits an HE frame as a response framewithout performing CCA within a TXOP, the SR field of the HE frame maybe based on the most recently received SR field within the TXOP. Inparticular, the SR field of the frame to be transmitted may be set tothe SR field of the frame most recently received from a STA in the sameBSS, or the STA with which communication is occurring in the TXOP (i.e.,the TXOP holder).

In an embodiment, if no SR field was received prior to transmitting a HEframe as a response frame within the TXOP, the STA uses a default valuefor the SR field.

In an embodiment, if a STA transmits an HE frame as a response framewithout performing CCA within a TXOP, the SR field of the HE frame isbased on the most recent CCA threshold status performed by the STA.

In an embodiment, when a STA transmits an HE frame without performingCCA, the SR field of the HE frame is set to a predetermined value. Thepredetermined value may be a state that implies no change in CCAthreshold values.

FIG. 10 illustrates an embodiment of determining the contents of an SRfield within the same TXOP. In FIG. 10, STA1 has multiple framesbuffered to send. To initiate the transmission, STA1 performs CCA. AfterSTA1 assesses the wireless medium as IDLE during the CCA, STA1 transmitsa first frame 1012 to STA2, and the first frame 1012 sets a TXOPduration of T_TXOP.

At a predetermined time T1 after transmitting first frame 1012, STA1transmits a second frame 1014 without performing CCA becausetransmission of the second frame 1014 can be finished within TXOPduration. In this example, both first frame 1012 and second frame 1014use a frame format that includes SR fields 1032 and 1034, respectively,in the physical layer header part of the frames.

The SR field of first frame 1012 is determined based on CCA thresholdadjustment during the channel assessment. In an embodiment, the SR field1034 of second frame 1014 is also determined based on the same initialCCA. In one embodiment, the SR field 1012 of first frame 1012 isidentical to the SR field 1034 of second frame 1014 and SR field 1036 ofthird frame 1016. STA1 may use the same CCA values for all SR fields inthe same TXOP.

In another embodiment, the SR field 1034 of second frame 1014 isfunction of the value of SR field 1032 of first frame 1012. In such anembodiment, additional parameters can be considered when determiningsubsequent SR fields 1034 and 1036. One additional parameter that may beconsidered is the transmission bandwidth difference between first frame1012 and second frame 1014.

For example, if STA1 assesses a wireless medium to be IDLE by increasinga CCA threshold value for an OBSS frame, which is accompanied by areduction of STA1's transmission power, wherein the transmission powerreduction is indicated in the SR field of first frame 1012, thetransmission power reduction indicated in the SR field of second frame1014 shall not be lower than the transmission power reduction indicatedin the SR field of first frame 1012.

In another example, if the CCA level during the initial CCA is indicatedin the SR field 1032 of first frame 1012, the same CCA level isindicated in the SR field 1034 of second frame 1014, as well as the SRfield 1036 of third frame 1016.

Or, if interference level accepted (ILA) during the CCA is indicated inthe SR field 1032 of first frame 1012, the same interference levelaccepted is indicated in the SR field 1034 of second frame 1014, as wellas the SR field 1036 of third frame 1016.

In addition, FIG. 10 shows a fourth frame 1028 transmitted by STA2 thatincludes an SR field 1038. Like SR fields 1032, 1034 and 1036, SR field1038 may be based on the CCA performed by STA1 immediately prior to theTXOP. SR field 1038 may be the same as all of the SR fields in a TXOP,or may have values that are adjusted based on additional parameters.

In an embodiment, T1 of FIG. 10 is a short underframe space (SIFS).

FIG. 11A shows another embodiment of determining an SR field for framesin the same TXOP. In FIG. 11A, first frame 1112 follows a frame formatthat does not have an SR field in the physical layer header part of theframe, such as a non-HT frame format. However, second frame 1114 followsa frame format that has SR field in the physical layer header part ofthe frame, such as HE frame format defined in IEEE 802.11 Task Group ax.

In one embodiment, the SR field of second frame 1114 is determined basedon CCA threshold adjustment during the initial CCA, and may simplyreflect the CCA threshold used for the CCA. In another embodiment, theSR field of second frame 1134 is a function of the CCA thresholdadjustment performed in the initial CCA and a transmission parameterdifference between a transmission parameter of first frame 1112 andsecond frame 1114. The transmission parameter may be a bandwidth value.

For example, if STA1 assesses a wireless medium to be IDLE by increasinga CCA threshold for OBSS frame, which is accompanied by reduction in theSTA's transmission power, the transmission power reduction indicated inthe SR field of second frame 1014 shall not be lower than that usedduring CCA.

In another example, if STA1 assesses a wireless medium to be IDLE byincreasing CCA threshold for OBSS frame, which is accompanied byreduction in the transmission power, the transmission power reductionindicated in the SR field of second frame 1014 is the same with thatused during CCA.

In addition, FIG. 11A shows a fourth frame 1128 transmitted by STA2 thatincludes an SR field 1138. Like SR fields 1134 and 1136, the contents ofSR field 1138 may be based on the CCA performed by STA1 immediatelyprior to the TXOP. SR field 1138 may be the same as all of the SR fieldsin the TXOP, or may include values that are adjusted based on additionalparameters. SR field 1138 may be present in fourth frame 1128 so long asthe format of fourth frame 1128 supports the SR field and receives aframe from STA1 that does include an SR field, regardless of whetherfirst frame 1112 has a format that supports SR fields.

FIG. 11B shows another embodiment of determining an SR field for framesin the same TXOP. In FIG. 11A, first frame 1112 uses a frame format thatdoes not have an SR field in the physical layer header part of theframe, such as a non-HT frame format.

In FIG. 11B, STA1 has a frame buffered to send to STA2. To initiate thetransmission, STA1 performs CCA. After STA1 assesses the wireless mediumas IDLE during CCA, STA1 transmits the first frame 1112 to STA2, whereinfirst frame 1112 sets a TXOP duration.

In a predetermined time (T1) after transmitting the first frame 1112,STA2 transmits a response frame 1128 to STA1. In this example, firstframe 1112 uses a frame format that does not have an SR field in thephysical layer header part of the frame, such as non-HT frame format.However, response frame 1138 uses a frame format that has SR subfield inthe physical layer header part of the frame, such as HE frame formatdefined in IEEE 802.11 Task Group ax.

In one embodiment, the SR subfield of response frame 1128 is set to apredetermined value. In another embodiment, the predetermined value is astate that implies no CCA threshold adjustment is made. In anotherembodiment, the predetermined value is broadcasted by a serving APbefore transmitting response frame 1128.

In another embodiment, the predetermined value is determined when STA2is associated to the serving AP. In another embodiment, the serving APperiodically broadcasts the predetermined value in a Beacon frame. Inanother embodiment, STA2 decides the SR field 1138 of second frame 1128based on the most recently used CCA threshold adjustment value. Inanother embodiment, STA2 decides the SR field of response frame 1128based on based on the SR field of a frame from STA1 that is the mostrecently successfully received frame that comprises the SR information.

Spatial Reuse Fields in Multiuser Transmissions

In order to support higher throughput, some wireless communicationsystems use multi-user (MU) simultaneous transmission and reception.Examples of MU technologies include OFDMA and Multi-UserMultiple-Input-Multiple-Output (MU-MIMO).

FIG. 12 shows an example of an uplink MU transmission. In the example ofFIG. 12, the AP performs CCA, establishes a TXOP, and multicasts atrigger frame 1212 to STA1, STA2, and STA3 in the AP's BSS. After apredetermined time T1, the STAs transmit their own uplink MU frames1224, 1234 and 1244.

Because all the participating STAs received the trigger frame 1212almost simultaneously and all three STAs used the same delay (T1), thetransmission time of all three STAs can be synchronized, and thereforeSTA transmissions 1224, 1234 and 1244 are synchronized as well. The APmay then transmit an ACK frame 1216.

The UL frames from the participating STAs may include preambles thatextend across the same part of the frequency spectrum as all other STAs.Returning to the example of FIG. 6, even though data transmissions 608of the transmitting STAs are separated in frequency, the preamble parts602, 604 and 606 share the same frequencies.

Therefore, in order to avoid interference, the STA may all transmit thesame preamble information at the same time. Accordingly, in FIG. 12, thedata in preambles 1227, 1237 and 1247 is the same. The information forSR in the physical layer header may be included in the HE-SIG-A field sothat other STAs may use the HE-SIG-A field to perform channelassessment.

Therefore, in an embodiment, all participating STAs of an UL MUtransmission apply the same SR related adjustment, such that SR relatedfields in the physical layer header part from different STAs are thesame among participating STAs. In an embodiment, all participating STAsof an UL MU transmission apply the same SR value to the SR field suchthat the indicated value disallows other unintended recipients of the ULMU frame to attempt to access the medium using aggressive CCA or spatialreuse techniques. In other words, the value indicates that theunintended recipients shall use legacy CCA thresholds and legacy channelaccess rules to access the medium during the UL MU transmission.

In an embodiment, when a STA assess the wireless medium for an UL MUtransmission, the STA uses an OBSS_PD value without any adjustment. Inother words, the STA may use a default or default OBSS_PD value for aCCA part of an SR field.

In an embodiment, when an AP schedules an UL MU transmission, the APassigns an MCS level with same level of interference margin for allscheduled STAs.

In an embodiment, all scheduled STAs use the same level of transmissionpower reduction for an UL MU transmission.

In an embodiment, all scheduled STAs for an UL MU transmission use thesame level of OBSS_PD threshold value adjustment. In other words, theCCA data in the SR field may be the same for all STAs for an UL MUtransmission.

In an embodiment, the SR related adjustment indicated in the physicallayer header part of UL MU PPDU is linked to the SR related adjustmentof an immediately preceding frame that includes the trigger information.Thus, SR data in headers 1227, 1237 and 1247 may be derived from SR datain trigger frame 1212. The trigger frame 1212 includes resourceallocation information for the wireless stations STA1, STA2, and STA3 toparticipate in MU uplink transmissions to the AP (e.g., an OFDMA and/orMU-MIMO transmission).

FIG. 13 shows an embodiment of MU transmissions. In FIG. 13, the APperforms CCA and establishes a TXOP for MU transmission for STA1, STA2and STA3. The MU transmission is initiated by the AP's trigger frame1312, which includes SR data 1318. The SR data 1318 may include, forexample, CCA information based on a CCA performed by the AP immediatelyprior to the TXOP, or CCA information based on default values.

The STAs in the MU session consider the SR information 1318 whendeciding wireless channel assessment for the UL MU transmissions. Inparticular, the SR information 1318 adjusts CCA threshold values foreach participating STA. Using the adjusted CCA threshold, STA1 and STA3assess the wireless medium to be IDLE, but STA2 assesses the wirelessmedium to be BUSY.

Therefore, only STA1 and STA3 transmits UL MU frames a predeterminedtime (T1) after receiving the Trigger frame 1312. A physical layerheader part of the UL MU frames includes SR fields 1350 whose contentsare determined based on the SR information 1318 delivered in the Triggerframe 1312.

FIG. 14 shows an embodiment in which two STAs, STA1 and STA2, areincluded in a TXOP for MU transmission from an AP. The AP initiates theTXOP with a HE trigger frame 1412 that includes first SR information (SRAP) 1410 that is indicated in the HE-SIG-A field of the trigger frame.The AP may calculate second SR information (SR STA) 1418 that is afunction of first SR information 1410, and include the second SRinformation in the payload of the trigger frame 1412.

Subsequently, STA1 and STA2 include the second SR information 1450 inthe HE-SIG-A field of their UL MU frames 1424 and 1434, and transmit ULMU frame in T1 time after receiving the Trigger frame.

In an embodiment, when the AP assesses the wireless medium fortransmission of the trigger frame 1412, the AP adjusts its CCA thresholdvalue depending on its interference situation, and the first SRinformation 1410 is a function of the AP's CCA threshold valueadjustment. In an embodiment, the second SR information 1418 isidentical to the first SR information 1410.

FIG. 15 illustrates another embodiment of SR fields in a MUtransmission. In the embodiment of FIG. 15, a TXOP for MU transmissionis initiated by a HE trigger frame 1512 from the AP in which first SRinformation 1510 is included in a header of the trigger frame.

After receiving the trigger frame 1510, participating STAs STA1 and STA2include the same second SR information 1550 in transmitted frames 1524and 1534, respectively. In an embodiment, the second SR information 1550is a predetermined function of first SR information 1510, such thatdifferent STA can derive the same second SR information.

In an embodiment, when the AP assesses the wireless medium fortransmission of the trigger frame 1512, the AP adjusts its CCA thresholdvalue depending on the interference situation, and the first SRinformation 1510 is a function of the AP's CCA threshold valueadjustment. In an embodiment, the second SR information 1550 isidentical to the first SR information 1510.

FIG. 16 illustrates another embodiment of SR fields in a MUtransmission. In the embodiment of FIG. 16, a MU TXOP is initiated by atrigger frame 1612 from the AP that is not an HE trigger frame. Forexample, the trigger frame 1612 may have a non-HT/HT format or a VHTformat. Accordingly, the header of trigger frame 1618 does not includeSR information.

When the AP assesses the wireless medium for transmission of the triggerframe 1612, the AP adjusts its CCA threshold value depending on theinterference situation. The AP then calculates SR information 1618 to beincluded in the HE-SIG-A field of UL MU frames 1624 and 1634, which is afunction of the AP's CCA threshold value adjustment, and includes the SRinformation in the payload of the trigger frame 1612. The participatingSTAs STA1 and STA2 include second SR information 1650 in the HE-SIG-Afields of their UL MU frames 1624 and 1634, and transmit the frames.

FIG. 17 shows a MU process 1700 according to an embodiment that may beperformed by an AP. An AP performs clear channel assessment at 51702 anddetermines that the wireless medium is IDLE under a first CCA thresholdcondition. The AP then calculates first SR information at S1704 based onthe first CCA threshold condition, and transmits a frame that includessecond SR information based on the first SR information to a pluralityof STAs at 51706. The first and second SR information may be the same,or the second SR information may be a function of the first SRinformation.

The AP receives frames from one or more of the plurality of STAs atS1708. The frames may include SR information that may be the sameinformation as the SR information transmitted to the STAs by the AP, ora function of the SR information transmitted to the STAs by the AP.

In an embodiment, a CCA condition that may be included in SR informationis increasing an AP's CCA threshold value by decreasing the serving AP'stransmission power. The SR information may relate to the amount by whichthe serving AP decreases its transmission power.

In an embodiment, the same condition is maintained for the first CCAthreshold condition throughout a beacon period.

In an embodiment, the first CCA threshold condition is only related withadjustment of a CCA threshold when the serving AP identifies a start ofa frame, and the frame is transmitted by an OBSS STA.

In an embodiment, information on the first SR information is included inthe physical layer payload of the first frame.

In an embodiment, the SR information relates to transmission power.

In an embodiment, the SR information relates to an accepted interferencelevel.

In an embodiment, the SR information relates to a CCA level.

In an embodiment, the physical layer header of the first frame comprisesSR information that is based on the first CCA threshold condition.

The SR information transmitted by the AP may relate to the SRinformation in a frame transmitted by a STA through the followingrelationship: (AP SR information)=(STA SR information)+Delta. Delta maybe a function of a number of STA that the serving AP schedules for UL MUtransmission.

From the perspective of a STA, an embodiment of a process for a MU SRfield may include receiving the first frame by one or more target STAs,calculating by one or more target STAs, the first SR information basedon second SR information, and transmitting, by one or more target STAs,a second frame, wherein the physical layer header of the second framecomprises the first SR information.

In another embodiment, a method for UL MU transmission comprisestransmitting, by a serving AP, a first frame to more than one targetSTAs, wherein a physical layer header of the first frame comprises asecond SR information; and receiving, by the serving AP, a second framefrom one or target STAs in predetermined time after transmitting thefirst frame, wherein the physical layer header of the second framecomprises a first SR information, wherein the first SR information isbased on the second SR information. The first SR information may beidentical to the second SR information. In an embodiment, the first SRinformation and the second SR information has the followingrelationship: (first SR information)=(second SR information)+Delta.Delta may be a function of the number of stations that the serving APschedules for UL MU transmission.

Embodiments of the present disclosure may be implemented in the form ofprogram instructions executable through various computer means, such asa processor or microcontroller, and recorded in a non-transitorycomputer-readable medium. The non-transitory computer-readable mediummay include one or more of program instructions, data files, datastructures, and the like. The program instructions may be adapted toexecute the processes and to generate and decode the frames describedherein when executed on a device such as the wireless devices shown inFIG. 1.

In an embodiment, the non-transitory computer-readable medium mayinclude a read only memory (ROM), a random access memory (RAM), or aflash memory. In an embodiment, the non-transitory computer-readablemedium may include a magnetic, optical, or magneto-optical disc such asa hard disk drive, a floppy disc, a CD-ROM, and the like.

While this invention has been described in connection with what ispresently considered to be practical embodiments, embodiments are notlimited to the disclosed embodiments, but, on the contrary, may includevarious modifications and equivalent arrangements included within thespirit and scope of the appended claims. The order of operationsdescribed in a process is illustrative and some operations may bere-ordered or not performed in various embodiments. Further, two or moreembodiments may be combined.

What is claimed is:
 1. A method for performing a multi-user uplinktransmission, the method comprising: receiving, by a first wirelessstation from a second wireless station, a first frame including a firstspatial reuse field and a second spatial reuse field; analyzing, by thefirst wireless station, the first spatial reuse field of the firstframe; generating, by the first wireless station, a second frame,wherein the second frame is a data frame and includes a spatial reusefield that is generated based on the analysis of the first spatial reusefield of the first frame; and transmitting, by the first wirelessstation, the second frame, wherein the first frame and the second frameare within a same transmission opportunity (TXOP) and the first frame istransmitted prior to the second frame during the TXOP, wherein thesecond spatial reuse field of the first frame contains informationregarding spatial reuse different from that of the first spatial reusefield of the first frame, wherein the first frame is a trigger frame,and wherein the transmitting of the second frame by the first wirelessstation is part of an uplink multi-user transmission.
 2. The method ofclaim 1, wherein a value in the first spatial reuse field is included inthe second spatial reuse frame.
 3. The method of claim 1, wherein thespatial reuse field of the second frame includes a transmit powerindication.
 4. A wireless device comprising: a transmitter circuit; anda receiver circuit, and a baseband processor, wherein the wirelessdevice is configured to: receive, by the receiver circuit from a secondwireless station, a first frame including a first spatial reuse fieldand a second spatial reuse field; analyze, by the wireless device usingthe baseband processor, the first spatial reuse field of the firstframe; generate, by the baseband processor, a second frame, wherein thesecond frame is a data frame and includes a spatial reuse field that isgenerated based on the analysis of the first spatial reuse field of thefirst frame; and transmit, by the transmitter circuit, the second frame,wherein the first frame and the second frame are within a sametransmission opportunity (TXOP) and the first frame is transmitted priorto the second frame during the TXOP, and wherein the second spatialreuse field of the first frame contains information regarding spatialreuse different from that of the first spatial reuse field of the firstframe.
 5. The wireless device of claim 4, wherein the first frame is atrigger frame, and wherein the wireless device transmits the secondframe as part of an uplink multi-user transmission.
 6. The wirelessdevice of claim 5, wherein a value in the first spatial reuse field isincluded in the second spatial reuse frame.
 7. The wireless device ofclaim 5, wherein the spatial reuse field of the second frame includes atransmit power indication.